In the past, splints have been made from a variety of materials, chiefly plaster, metal and plastic. Splints, in terms of duration of use, are of three types: emergency splints, short term splints and medium to long term splints. Emergency splints are temporary in use; their primary objective is to immobilize an injured part while x-rays are taken and are usually in place only a few hours. Short-term splints are often used until swelling of an injured limb subsides after which the limb may be enclosed in an orthopedic cast. The period of use of a short term splint generally is from 2 to 5 days. Since the duration of use of emergency and short-term splints is limited, the splints need not be especially durable. Such splints usually are made of plaster of paris, which although not strong and durable is inexpensive.
Long term splints, because of the need for durability, are made of materials such as metals, plastic coated metals (aluminum, for example), and thermoforming plastics. There are two categories of such splints: pre-formed to a general shape of a limb and moldable splints that can be shaped to conform exactly to the patient's limb. Pre-formed splints do not generally conform exactly to an individual patient's limb resulting in a poor fit that is uncomfortable for the patient and may not be adequately immobilize, support and protect the injured member. The moldable splints while more conformable are not as rigid and strong as pre-formed splints. Some moldable materials are rendered flexible by heating and while hot can be molded into a variety of shapes and so conform well. However, they lack strength, are expensive and require considerable time to cut, trim and mold. Devising splints from these materials requires considerably skill in the use of wood and metal working tools, high temperature ovens, heat guns, hot water baths, solvents, and grinding tools. Generally the skills and equipment needed call for the services of an orthotist and a fully equipped appliance room. Cast rooms are not equipped to work with such materials.
Other moldable splints have been reported. In most cases these are dependent on solvents to soften the stiffening agent and after molding the solvent must be evaporated. Since most of these solvents are flammable, there is a constant fire hazard. In many cases, solvents useable can be toxic upon contact with the skin and this too is a deficiency. A further deficiency is that the evaporation of the solvent is necessarily a very slow process.
Another form of contour splint depends on a thermo-setting resin. Such resins are usually two component systems involving the monomer and catalytic polymerization agent. It is necessary in order to use these resins to mix the two components, coat the splint while molded to the contours of the limb and then polymerize by the use of heat. Not only is this process slow but the use of heat is a limitation since the polymerization must be done on the limb.
Photocurable materials are on the market for use in casts, as described by Beightol U.S. Pat. No. 3,421,501 and Corvi et al. U.S. Pat. No. 3,881,473. In these casts a tape impregnated with a photosensitive resin system is wrapped around the limb. Rigidity is obtained by the laminating effect of winding the tape in several layers. The Corvi modification achieved a quicker cure by controlling the size of the openings in the tape in order to permit light penetration through the various layers. For a splint, it is necessary to have a limited amount of lamination in order to permit moldability, easy and fast curing and ability to trim the splint to conform in size to the limb. Thus, one cannot use the tape used to make casts. In order to get rigidity, these need a multilayer application. When used in single or even double layers, little or no rigidity is obtained.